1. Field of the Invention
This invention relates to an electromagnetic relay. The invention also relates to a method for producing such an electromagnetic relay.
2. Description of the Related Art
An electromagnetic relay is required to provide for passage and blockage of a large current of high-voltage direct current, when it is used for an industrial power supply equipment, such as an uninterruptible power supply (UPS) installed in a telecommunication base station, or for a power conditioner or a rechargeable battery in a fuel cell system or a solar power system. In an electromagnetic relay in these applications, it is necessary to provide a sufficient movable range of movable contacts so as to switch the power source on and off, and it tends to complicate the configuration or increase the size in order to improve heat dissipation capacity and durability. JP 2010-44973 A describes an electromagnetic relay with an actuating part having an improved form in order to address such issues.
It has been known in an electromagnetic relay that arc discharge occurs when a movable contact moves apart from a fixed contact or when the movable contact approaches to the fixed contact. This phenomenon becomes more remarkable, as a voltage applied to the electromagnetic relay becomes higher or an electric current passing through the electromagnetic relay becomes larger. The arc discharge could result in damaging the contacts or decreasing blockage capability of the electric current.
An electromagnetic relay has been known, including a bar-shaped magnet having a length equal to or greater than the distance between a pair of fixed contacts (or a pair of movable contacts), the magnet being provided opposite to a gap between the fixed contacts and the movable contacts. (See JP 2000-195402 A, for example.). The electromagnetic relay is designed to generate a magnetic field perpendicular to the gap between the fixed contacts and the movable contacts by providing the magnet inside the side wall of a cover enclosing the respective parts, thereby cutting off the arc discharge. In this configuration, the magnet is placed on a side wall of the cover by insert molding, or in a pocket which has been formed in the cover prior to placement of the magnet.
There is a need for an inexpensive electromagnetic relay having a simpler configuration, which allows for passage and blockage of a high voltage and/or a large current.